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United States 
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Forest Service 

Miscellaneous 
Publication 
Number 1548 



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USDA 



Ecoregions Map 
of North America 

Explanatory Note 



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Historic, archived document 

Do not assume content reflects current 
scientific knowledge, policies, or practices. 






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Ecoregions Map 
of North America 

Explanatory Note 



May 1 998 

Prepared in cooperation with 
The Nature Conservancy and the 
U.S. Geological Survey 

by 

Robert G. Bailey, 1 Geographer 
Ecosystem Management Coordination Staff 
USDA Forest Service, Washington, DC 



' Address: Ecosystem Management Analysis Center, USDA Forest Service, 
3825 East Mulberry Street, Fort Collins, CO 80524 USA. 



Bailey, Robert G. 1998. Ecoregions map of North America: 
Explanatory note. Misc. Publ. 1548. Washington, DC: 
USD A Forest Service. 10 p. 

This publication explains the basis of map units shown 
on the second (revised) edition of the map, Ecoregions 
of North America (Bailey 1997). Climate diagrams are 
included to help explain the conditions that create a 
particular ecoregion. The revised map at a scale of 
1:15.000.000 accompanies this explanatory note. 

Keywords: ecosystem geography, ecoregions, North America 



Acknowledgements 

I am indebted to John M. Crowley, who began the task of 
classifying the natural ecosystems of the continent and their 
distribution. Recognition should also go to Denny Gross- 
man. Chief Ecologist of The Nature Conservancy, for his 
support. The first draft of the map was made by Jon Havens 
of LCT Graphics. I am most grateful to the U.S. Geological 
Survey, which helped fund the preparation of the base map. 
As always, it has been a pleasure to work with Loreen Utz 
and Dave Dee of the National Mapping Division of the Sur- 
vey, who did the final map compilation and cartography. 



Ecoregions Map of North America: Explanatory Note 



Land management is undergoing enormous change: away from managing single 
resources to managing ecosystems. An ecosystem is an area, of any size, in which 
there is a distinctive association of causally interconnected features. A change in one 
feature causes a change within another with corresponding geographic distribution, as 
when certain vegetation and soil types occur together with certain types of climate. To 
manage ecosystems we must understand where they are located and why. We need to 
do this at multiple scales because ecosystems occur in a hierarchy of varying sizes. 
Ecosystems of regional extent, those at the macro scale, are called ecosystem regions, 
or ecoregions. Ecoregions are useful in addressing environmental issues over large 
areas, i.e., issues that transcend agency, watershed, and political boundaries and 
borders, such as air pollution, declining anadromous fisheries, forest disease, or 
threats to biodiversity. 

The second (revised) edition of the map, Ecoregions of North America (Bailey 1997), 
is the result of cooperation among the USDA Forest Service, The Nature Conservan- 
cy, and the U.S. Geological Survey. The first edition of the map was 
published in 1981 by the U.S. Fish and Wildlife Service (Bailey and Cushwa 1981). 
Since that time, more ecological mapping has been earned out in some parts of the 
continent (e.g., Dinerstein and others 1995) and new or updated national maps have 
been compiled (e.g., Ecoregions Working Group 1989: Bailey 1994, 1995); it was 
therefore decided that a second revised edition of the map should be published. It has 
been compiled from a number of sources, both new since 1981 and older; the most 
important of which are listed in the Sources. 

The map uses a worldwide classification developed by Bailey (1983, 1989. 1998) and 
Bailey and Hogg (1986) from concepts advanced by Crowley (1967). The general 
principle followed has been to identify ecosystem regions of continental scale based 
on macroclimate (i.e., the climate that lies just beyond the local modifying irregulari- 
ties of landform and vegetation). Macroclimates are among the most significant 
factors affecting the distribution of life on earth. As the macroclimate changes, the 
other components of the ecosystem change in response. Macroclimates influence soil 
formation and help shape surface topography, as well as affecting the suitability of a 
given system for human habitation. As a result, ecosystems of different macroclimates 
differ significantly. 

Based on macroclimatic conditions and on the prevailing plant formations determined 
by those conditions, I subdivided the continent into ecoregions with three levels of 
detail. Of these the broadest, domains, and within them divisions, are based largely on 
the broad ecological climate zones of W. Koppen (as modified by Trewartha 1968, 
Appendix 1). : Thermal and moisture limits for plant growth determine their 



2 Other methods for mapping zones at the global scale are those of Thornthwaite (1931, 1933). Holdridge (1947). and 
Walter and Box (1976). All methods appear to work better in some areas than in others, and to have gained their own 
adherents. I chose the Koppen system as the basis for ecoregion delineation because it has become the international 
standard for geographical purposes. 



boundaries. Domains are groups of related climates. There are four groups. Three are 
humid, thermally differentiated: polar, with no warm season; humid temperate, rainy 
with mild to severe winters; humid tropical, rainy with no winters. The fourth, dry, is 
defined on the basis of moisture alone, and transects the otherwise humid domains. 
Within these groups are 15 types of climate based on seasonality of precipitation or 
on degree of dryness or cold, e.g., within the humid tropical domain, rainforests with 
year-round precipitation can be distinguished from savannas with winter drought. 
Divisions correspond to these types. Each division is clearly defined by a particular 
type of climate diagram that helps explain the conditions that create them (see Appen- 
dix 2 for stations thought to be representative of each division). For more informa- 
tion, including illustrated, detailed descriptions of the divisions, see my 
related book, Ecoregions (Bailey 1998). 

The climate is not completely uniform within divisions, so that a further subdivision 
can be undertaken. Within the dry climates, for example, there is a wide range of 
degree of aridity, ranging from very dry deserts through transitional levels of aridity 
in the direction of adjacent moist climates. We refer to these as climate subtypes. The 
subtypes largely correspond to major plant formations (for example, broadleaved 
forest), which are delimited on the basis of macro features of the vegetation by 
concentrating on the life-form of the plants. They form the basis for subdividing 
ecoregion divisions into provinces, and are based on a number of sources, including 
a world map of landscape types (Milanova and Kushlin 1993). 

The arrangement of the ecological climate zones depends largely on latitude and 
continental position. This pattern, however, is overlain by mountain ranges, which cut 
across latitudinally oriented climatic zones to create their own ecosystems. Altitude 
creates characteristic ecological zones that are variations of the lowland climate. 
Mountains show typical climatic characteristics, depending on their location in the 
overall pattern of global climatic zones. The mountain ranges of Central America, for 
example, experience the same year-round, high-energy input, and seasonal moisture 
regime consisting of a relatively dry winter and rainy summer typical of their neigh- 
boring lowlands (see the diagrams for Mexico City and San Salvador in Appendix 2). 

Every mountain within a climatic zone has a typical sequence of altitudinal belts, 
with different ecosystems at successive levels: generally montane, alpine, and nival, 
but exhibiting considerable differences according to the zone where they occur. When 
a mountain extends over two or more climatic zones it produces different vertical 
zonation patterns. Mountains exhibiting altitudinal zonation and the climatic regime 
of the adjacent lowlands are distinguished according to the character of the zonation 
by listing the altitudinal zones present. Such mountainous environments are termed 
mountain provinces. 

Thirty-four provinces and 29 mountain provinces are differentiated and represented 
on the present map (within 15 divisions and four domains). 



Note that these ecoclimatic zones are greatly simplified and do not show soil-related 
or human influences. The only major exception is where intrazonal contrasts (related 
to groundwater) form riverine forests along the lower Mississippi River valley. Also, 
the boundaries shown are only approximate and give a broad-brush picture. The actual 
boundaries may be very irregular and much modified by human interference. 

The similar colors on the map show the major climatic zones: the mountains in each 
zone are shown by pattern. The names of the provinces retain the names of the most 
obvious vegetation indicator: tundra, broadleafed forest, etc. The terms used in 
describing the provinces may not be familiar and so need explanation. They are listed 
in the Glossary. In mountain areas, the altitudinal zonality-types are named from the 
lower- and upper-elevation (subnival) belts: (e.g., forest - alpine meadow), which vary 
considerably according to the zones in which they occur. Each type corresponds to a 
typical sequence of altitudinal belts. 

When it is necessary to emphasize the existence of intermediate belts in the structure 
of similar spectra, the name of the most characteristic intermediate belt is added to 
the designation; for example, mixed forest - coniferous forest - tundra. In low- and 
medium-relief mountains, the zonal spectra are incomplete. In such cases, the type is 
designated by the character of the lower belt. More details are presented elsewhere 
(Bailey 1983, 1996). 

A digital version of the map is available in ARC/INFO format from the USDA-Forest 
Service, Ecosystem Management Analysis Center, on a cost-of-production basis. 



Glossary 



Broadleafed — with leaves other than linear in outline: as 

opposed to needleleafed or grass-like (graminoid). 
Coniferous — trees bearing cones and commonly having 

needleshaped leaves usually retained during the year; 

adapted to moisture deficiency due to frozen ground or 

soils that are not moisture-retentive. 
Deciduous — woody plants, or pertaining to woody plants, that 

seasonally lose all their leaves and become temporarily 

bare-stemmed. 
Desert — supporting vegetation of plants so widely spaced. 

or sparse, that enough of the substratum shows through to 

give the dominant tone to the landscape. 
Dry steppe — with 6-7 arid months in each year. 
Evergreen — plants, or pertaining to plants, which remain 
green in parts of the year around, either by retaining at least 

some of their leaves at all times, or by having green stems 

which carry on the principal photosynthetic functions. 
Forest — open or closed vegetation with the principal layer 

consisting of trees averaging more than 5 m in height. 
Forest-steppe — intermingling of steppe and groves or strips 

of trees. 
Forest-tundra — intermingling of tundra and groves or strips 

of trees. 
Heath — an area of largely treeless country, dominated by 

various grasses able to thrive on poor acidic soils, often 

accompanied by dwarf shrubs. 
Meadow — closed herbaceous vegetation, commonly in 

stands of rather limited extent, or at least not usually 

applied to extensive grasslands. 
Mixed forest — forest with both needleleafed and 

broadleafed trees. 



Nival — of or relating to a region of perennial snow. 

Open woodland (also called steppe forest and woodland- 
savanna) — open forest with lower layers also open, 
having the trees or tufts of vegetation discrete but 
averaging less than their diameter apart. 

Paramo — the alpine belt in the wet tropics. 

Prairie — consist of tall grasses, mostly exceeding 1 m in 
height, comprising the dominant herbs, with subdomi- 
nant forbs (broadleafed herbs). 

Riverine forest (also called galeria and floodplain forest) — 
dense tropical, subtropical, or prairie, forest living along 
the banks of a river. 

Savanna — closed grass or other predominantly herbaceous 
vegetation with scattered or widely-spaced woody plants 
usually including some low trees. 

Semidesert (also called half-desert) — is an area of 

xerophytic shrubby vegetation with a poorly-developed 
herbaceous lower layer, e.g., sagebrush. 

Semi-evergreen forest (also called a monsoon forest) — 
where many, although not all, of the trees lose their 
leaves; adaptation to a dry season in the tropics. 

Shrub — a woody plant less than 5 m high. 

Steppe (also called shortgrass prairie) — open herbaceous 
vegetation, less than 1 m high, with the tufts or plants 
discrete, yet sufficiently close together to dominate the 
landscape. 

Tayga (also spelled taiga) — a parkland or savanna with 
needleleafed (usually evergreen) low trees and shrubs. 

Tundra — slow-growing, low-formation, mainly closed 
vegetation of dwarf-shrubs, graminoids. and cryp- 
tograms, beyond the subpolar or alpine tree-line. 



Sources 



The sources listed below have been consulted during the 
process of creating and updating the second edition. 

Bailey, R.G. 1983. Delineation of ecosystem regions. Envi- 
ronmental Management 7: 365-373. 

Bailey, R.G. 1989. Explanatory supplement to ecoregions 
map of the continents. Environmental Conservation 
16:307-309 with separate map at 1:30,000,000. 

Bailey, R.G. 1994. Map: Ecoregions of the United States 
(rev.). Washington, DC: USDA Forest Service. 
1:7,500,000. 

Bailey, R.G. 1995. Description of the ecoregions of the Unit- 
ed States. 2d ed. rev. and expanded (1st ed. 1980). Misc. 
Publ. 1391 (rev.). Washington, DC: USDA Forest Ser- 
vice. 108 p. with separate map at 1:7.500.000. 

Bailey, R.G. 1996. Ecosystem geography. New York: 
Springer- Verlag. 216 p. 

Bailey, R.G. 1997. Map: Ecoregions of North America 

(rev.). Washington, DC: USDA Forest Service in coopera- 
tion with The Nature Conservancy and the U.S. Geologi- 
cal Survey. 1:15,000,000. 

Bailey. R.G. 1998. Ecoregions: the ecosystem geography of the 
oceans and continents. New York: Springer- Verlag. 192 p. 

Bailey, R.G.; Cushwa, C.T 1981. Map: Ecoregions of North 
America. FWS/OBS-81/29. Washington, DC: U.S. Fish 
and Wildlife Service. 1:12,000,000. 

Bailey, R.G.; Hogg, H.C. 1986. A world ecoregions map 
for resource reporting. Environmental Conservation 
13:195-202. 

Borchert, J.F. 1950. The climate of the central North Ameri- 
can grassland. Annals Association of American Geogra- 
phers. 40:1-39. 

Cleland. D.T.; Avers, P.E.; McNab, W.H.; Jensen, M.E.: Bai- 
ley, R.G.; King, T.; Russell, W.E. 1997. National 
hierarchical framework of ecological units. In: Boyce, 
M.S.; Haney, A., eds. Ecosystem management. New 
Haven. CT: Yale University Press: 181-200. 

Crowley, J.M. 1967. Biogeography [in Canada]. Canadian 
Geographer 11: 312-326. 

Dinerstein, E.; Olson, D.M.; Graham, D.J.; Webster, A.L; 
Primm, S.A.; Bookbinder. M.P; Ledec, G. 1995. A 
conservation assessment of the terrestrial ecoregions of 
Latin America and the Caribbean. Washington, DC: The 
World Bank in association with The World Wildlife Fund. 
129 p. with separate map at 1:15,000.000. 



Ecoregions Working Group. 1989. Ecoclimatic regions of 
Canada, first approximation. Ecological Land Classif. 
Series No. 23. Ottawa: Environment Canada. 119 p. with 
separate map at 1:7,500,000. 

Ewel, J.J.; Whitmore, J.L. 1973. The ecological life zones of 
Puerto Rico and the U.S. Virgin Islands. Forest Service 
Research Paper ITF-18. Rio Piedras, PR: Institute of 
Tropical Forestry. 72 p. with separate map at 1 :250,000. 

Eyre, S.R. 1963. Vegetation and soils: a world picture. 
Chicago: Aldine. 324 p. 

Fosberg. F.R.; Gamier, B.J.: Kuchler, AW. 1961. Delimita- 
tion of the humid tropics. Geographical Review 51:333- 
347 with separate maps at 1:60.000,000. 

Government of Canada. 1974. National atlas of Canada, 
vegetation regions. 4th ed. (rev.). Toronto: Macmillan: 
45-46. In association with the Department of Energy, 
Mines and Resources, and Information Canada, Ottawa. 
1:15,000.000. 

Hammond, E.H. 1954. Small-scale continental landform 
maps. Annals Association of American Geographers. 
44:33-42. 

Holdridge, L.R. 1947. Determination of world plant forma- 
tions from simple climatic data. Science 105:367-368. 

Koppen, W. 1931. Grundriss der klimakunde. Berlin: Walter 
de Gruyter. 388 p. 

Kuchler, A.W. 1964. Potential natural vegetation of the con- 
terminous United States (map and manual). American 
Geographical Society Special Publication 36. 116 p. with 
separate map at 1:3,168,000. 

Lobeck, A.K. 1948. Map: Physiographic provinces of North 
America. Maplewood NJ: Hammond. 1:12.000,000. 

Milanova, E.V.; Kushlin, A.V.. eds. 1993. World map of pre- 
sent-day landscapes: an explanatory note. Moscow: 
Moscow State University. 33 p. with separate map at 
1:15,000,000. 

Rowe, J.S. 1972. Forest regions of Canada. Canadian 
Forestry Service Publ. No. 1300. 172 pp. with separate 
map at 1:6,336.000. 

Schmithtisen, J. 1976. Atlas zur biogeographie. Mannheim- 
Wien-Zurich: Bibliographisches Institut. 33 p. 

Shelford, V.E. 1963. The ecology of North America. Urbana: 
University of Illinois Press. 610 p. 

Thornthwaite, C.W. 1931. The climates of North America 
according to a new classification. Geographical Review 
21:633-655 with separate map at 1:20.000.000. 



Thornthwaite. C.W. 1933. The climates of the Earth. Geo- 
graphical Review 23:433-440 with separate map at 
1:77,000.000. 

Trewartha, G.T. 1968. An introduction to climate. 4th ed. 
New York: McGraw-Hill. 408 p. 

Udvardy, M.D.F. 1975. A classification of the biogeographi- 
cal provinces of the world. Occasional Paper No. 18. 
Morges, Switzerland: International Union for Conserva- 
tion of Nature and Natural Resources. 48 p. 



Walter. H.: Box. E. 1976. Global classification of natural 
terrestrial ecosystems. Vegetatio 32:75-81. 

Walter. H.: Harnickell. E.; Mueller-Dombois. D. 1975. Cli- 
mate-diagram maps of the individual continents and the 
ecological climate regions of the Earth. Berlin: Springer- 
Verlag. 36 pp. with 9 maps. 

Walter. H.: Lieth. H. 1960-1967. Klimadiagramm Weltatlas. 
Jena. East Germany: G. Fischer Verlag. maps, diagrams, 
profiles. Irregular pagination. 



Appendix 1: Ecological climate zones" 



Koppen group and types 



Ecoregion equivalents 



A Tropical and humid climates 

Tropical wet (Ar) 
Tropical wet-dry (Aw) 



Humid tropical domain (400) 
Rainforest division (420) 
Savanna division (410) 



B Dry climates 

Tropical/subtropical semi-arid (BSh) 
Tropical/subtropical arid (BWh) 
Temperate semi-arid (BSk) 
Temperate arid (BWk) 



Dry domain (300) 

Tropical/subtropical steppe division (310) 
Tropical/subtropical desert division (320) 
Temperate steppe division (330) 
Temperate desert division (340) 



C Subtropical climates 

Subtropical dry summer (Cs) 
Humid subtropical (Cf) 

D Temperate climates 

Temperate oceanic (Do) 

Temperate continental, warm summer (Dca) 

Temperate continental, cool summer (Deb) 



Humid temperate domain (200) 
Mediterranean division (260) 
Subtropical division (230) 
Prairie division (250) b 

Marine division (240) 

Hot continental division (220) 

Prairie division (250) b 

Warm continental division (210) 

Prairie division (250) b 



E Boreal climates 

Subarctic (E) 



Polar domain (100) 
Subarctic division (130) 



F Polar climates 

Tundra (Ft) 
Ice Cap (Fi) 



Tundra division (120) 
Icecap division (110) 



Definitions and Boundaries of the Kbppen-Trewartha System 

Ar All months above 18°C and no dry season. 

Aw Same as Ar, but with 2 months dry in winter. 

BSh Potential evaporation exceeds precipitation, and all months above 0°C. 

BWh One-half the precipitation of BSh, and all months above 0°C. 

BSk Same as BSh, but with at least 1 month below 0°C. 

BWk Same as BWh, but with at least 1 month below 0°C. 

Cs 8 months 10°C, coldest month below 18°C, and summer dry. 

Cf Same as Cs, but no dry season. 

Do 4 to 7 months above 10°C, coldest month above 0°C. 

Dca 4 to 7 months above 10°C, coldest month below 0°C, and warmest month above 22°C. 

Deb Same as Dca, but warmest month below 22°C. 

E Up to 3 months above 10°C. 

Ft All months below 10°C. 

Fi All months below 0°C. 

A/C boundary = Equatorial limits of frost; in marine locations, the isotherm of 18°C for coolest month. 

C/D boundary = 8 months 10°C. 

D/E boundary = 4 months 10°C. 

E/F boundary = 10°C for warmest month. 

B/A, B/C, B/D. B/E boundary = Potential evaporation equals precipitation. 



Based on the Koppen system of classification (1931). as modified by G.T. Trewartha ( 19681. 
Koppen did not recognize the Prairie as a distinct climatic type. The ecoregion classification 
system represents it at the arid sides of the Cf. Dca, and Deb types, following Borchert ( 1950). 



8 



Appendix 2: Climate diagrams of representative climate stations (based on Walter and Lieth 1960-67, Walter and others 197 
Polar Domain 



o 



110 Icecap 

Eismitte, Greenland (3030 m) 
-30.0°C mm 



iiii 



mm 
20 



JFMAMJJASOND 
-10- 








120 Tundra 

Barrow, Alaska (4 m) 

-12.2 C C 104 mm 



nun 
B0 




130 Subarctic 

Ft Vermilion, Alberta (290 m) 
-1.8°C 323 mm 



mm 
60 




°C 
30 H 



M130 Subarctic 

Aishihik (966 m) 

-3.6°C 248 mm 



mm 
60 





M220 Hot Continental 

BoonejM. Carolina. ^(1016m) 




JFMAMJJASOND 



-10' 



-20 



250 Prairie 

Fargo, N. Dakota (273 m) 

4.9°C 476 mm 



mm 
300 
200 
100 




Humid Temperate Domain r 



210 Warm Continental 

Duluth, Minnesota (354 m) 
3.4°C /\ 755 mm 



300 

-200 

100 




-10 



JFMAMJJASOND 



-20' 



230 Subtropical 

Atlanta^Georgia (297 m) 

16.8°C 



mm 
300 
200 
100 




J r MAMJJASOND 







-10- 



-20 



260 Mediterranean 

Pasadena, California (263 m) 



mm 

300 
200 
100 




J FMAMJJASOND 



-10- 
-20- 



220 Hot Continental 

Ft. Wayne, Indiana (244 m) 
9.9°C 869 mm 




300 
200 
100 



-10- 



-20- 





240 Marine 

^Vancouver, British Columbia (8 rcj^" 




"~~\10.0°C 1050 mm f~ 


°c 




30- 


\ / 


20- 


\_/ 


10- 


i i i i i i i i i i 



mm 
300 
200 
100 



J MAMJJASOND 



10 



-20' 



M260 Mediterranean 

Jahoe, California (1900 m) 



mm 
300 

200 
100 




J — MAMJJASOND 



-10- 

-20-'- 



Dry Domain 



310 Tropical/Subtropical 
Steppe 

Abilene, ATexas (534 m] 
18.1°C /\ 622 mm 




_! I 1 1 I I L_ 



JFMAMJJASOND 



300 
200 
100 

30 

60 

40 

20 




-10 



-20 



M330 Temperate Steppe 

Pikes Peak, Colorado (4301 m) 
-7.0°C y\ P\ 752 mm 



mm 
300 

200 

1 00 




320 Tropical/Subtropical 
Desert 

Brawley, California (-36 m) 
22.0°C 58 mm 




JFMAMJJASOND 
-10- 



r 300 
200 

100 



-20' 



340 Temperate Desert 

Salt Lake City, Utah (1300 m) 
10.6°C 414 mm 




300 

200 
100 



330 Temperate Steppe 

Colorado Springs, Colorado (1855 m) 
8.7°C 363 mm 



mm 
300 
200 
100 




JFMAMJJASOND 



-10 
-20 



Humid Tropical Domain 



410 Savanna 

San Salvador, El Salvador (698 m) 
23.2°C _ 1770 mm 




mm 
300 
200 
100 



M410 Savanna 

Mexico City, Mexico (2280 m) 
15.6°C 588 mm 



J FMAMJJASOND 




mm 
300 
200 
100 



°c 

30 
20- 

10 



J FMAMJJASOND 







420 Rainforest 

Belize, Belize (5 m) 

29.5°C 1810 mm 



mm 

I- 300 

200 

100 




1_ J_ 



I I I I I 



J FMAMJJASOND 







Exp 


anation 




2 30- 

CO 

E 
^20- 

_cz 

§10- 

E 


Division 

Location (Altitude) 

Mean annual temp. Mean annual pptn. 

Relative period __ 

of drought -y£ ^s< ^ 


-60 I 

Q_ 

"o 

CD 

-40 o. 

-20 "1 

E 

cz 


5 l 


F M A M J J A S N 
Months 


3 S 



10 



Revised 



North America Ecoregions Map 

The USDA Forest Service recently published a revised version of the ecoregions 
map of North America by Robert G. Bailey in cooperation with The Nature 
Conservancy and the U.S. Geological Survey. This 29" x 32" full-color map shows, 
at a scale of 1:15,000,000, the division of the continent into a hierarchy of ecosystem 
regions. The map replaces the now outdated map of North America ecoregions 
which was issued in 1981 by the U.S. Fish and Wildlife Service. The revised map 
can be used to address environmental issues that transcend agency, watershed, and 
political boundaries and borders. 



Part of Ecoregions Map of North America, 1997 edition. Source scale 1:15,000,000 




-v (r Mil 



For a/ree copy, write the author at: 

USDA Forest Service 

Ecosystem Management 

3825 East Mulberry Street 

Fort Collins, Colorado 80524 USA 



10/97 




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all prohibited bases apply to all programs.) Persons with disabilities who require 
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DC 20250-9410 or call 202-720-5964 (voice or TDD). USDA is an equal opportunity 
provider and employer. 



U.S. DEPARTMENT OF AGRICULTURE 
FOREST SERVICE eo° 



70° 



60° 



160° 



170° 



50° 



180° 



170° 



40° 



160° 



20° 




| no | Icecap 

1 120 | Tundra 

[ 130 | Subarctic / 

1 210 | Warm Continental 

I 220 | Hot Continental 

I 230 | Subtropical 

I 240 | Marine 

I 250 | Prairie 

1 260 1 Mediterranean 

1 310 | Tropical/Subtropical Steppe 

| 320 | Tropical/Subtropical Desert 

j 330 1 Temperate Steppe 

Temperate Desert 
j 410 Savanna 
| 420 | Rainforest 

Mountains with altitudinal zonation 



100° 



90° 



Base from World Databank II 
Prepared by the U.S. Geological Survey 



ECOREGIONS OF NORTH AMERICA 

By Robert G. Bailey 

U.S. Department of Agriculture, Forest Service 

Washington, DC 

Jointly supported by the U.S. Forest Service and 
The Nature Conservancy, Conservation Science Division 

REVISED-1997 



INTERIOR - GEOLOGICAL SURVEY. RESTON. VA • 1998 



Representative climate station 
Boundary of domain 
Boundary of division 
Boundary of province 



ECOREGION PROVINCES 

100 POLAR DOMAIN 

110 ICECAP DIVISION 



in Glacial ice 



120 TUNDRA DIVISION 

I i2i | Ice and stoney deserts 
| 122 I Arctic tundras 
| 123 | Tundras 
Ml 2 TUN DRA MOUNTAINS 

KM12M Polar desert 



X44\ 



Tundra - polar desert 



j/M 123/1 Tundra - meadow 

['Ml 2jt| Oceanic meadow - heath 
130 SUBARCTIC DIVISION 

| i3i j Forest-tundras and open woodlands 

| 132 | Tayga (boreal forests) 
Ml 30 SUBARCTIC MOUNTAINS 

^mbi^J Open woodland - tundra 

[Mi32a^| Tayga - tundra, medium 

I'M 132b 1 ] Tayga - tundra, high 

200 HUMID TEMPERATE DOMAIN 

210 WARM CONTINENTAL DIVISION 

I 2ii | Mixed deciduous-coniferous forests 
M210 WARM CONTINENTAL MOUNTAINS 

[M2iia] Mixed forest - coniferous forest - tundra, medium 



^M2iibj Mixed forest - coniferous forest - tundra, high 
220 HOT CONTINENTAL DIVISION 
Broadleaved forests, oceanic 
Broadleaved forests, continental 



221a 



221b 



M220 HOT CONTINENTAL MOUNTAINS 



[M22i/| Deciduous or mixed forest - coniferous forest - meadow 



|^M222J Broadleaf forest - meadow 
230 SUBTROPICAL DIVISION 

231 Broadleaved-coniferous evergreen forests 

I 232 Coniferous-broadleaved semi-evergreen forests 
M230 SUBTROPICAL MOUNTAINS 

LM23n Mixed forest - meadow 

i / / /I 

240 MARINE DIVISION 

241 Mixed forests 
M240 MARINE MOUNTAINS 

iMMi'j Deciduous or mixed forest - coniferous forest - meadow 
[M242a] Forest - meadow, medium 
^M242bi Forest - meadow, high 



250 PRAIRIE DIVISION 

| 251 \ Forest-steppes and prairies 
I 252 | Prairies and savannas 
260 MEDITERRANEAN DIVISION 
| 261 j Dry steppe 

| 262 | Mediterranean hardleaved evergreen forests, open woodlands and shrub 
I 263 \ Redwood forests 

M260 MEDITERRANEAN MOUNTAINS 

[M26i^ Mixed forest - coniferous forest - alpine meadow 

yM262y\ Mediterranean woodland or shrub - mixed or coniferous forest - steppe or meadow 
Shrub or woodland - steppe - meadow 

300 DRY DOMAIN 
310 TROPICAL/SUBTROPICAL STEPPE DIVISION 

| 3ii j Coniferous open woodland and semideserts 

j 312 I Steppes 

| 313 j Steppes and shrubs 

| 314 Shortgrass steppes 
M310 TROPICAL/SUBTROPICAL STEPPE MOUNTAINS 

[-mmi^ Steppe or semidesert - mixed forest - alpine meadow or steppe 
320 TROPICAL/SUBTROPICAL DESERT DIVISION 

321 | Semideserts 
j 322 | Oceanic semideserts 
I 323 j Deserts on sand 
M320 TROPICAL/SUBTROPICAL DESERT MOUNTAINS 

Semidesert - shrub - open woodland - steppe or alpine meadow 
yyup^ Desert or semidesert - open woodland or shrub - desert or steppe 
330 TEMPERATE STEPPE DIVISION 
| 331 I Steppes 
| 332 I Dry steppes 
M330 TEMPERATE STEPPE MOUNTAINS 

Forest-steppe - coniferous forest - meadow - tundra 
Steppe - coniferous forest - tundra 
£m333^J Steppe - coniferous forest 

• M33J Steppe - open woodland - coniferous forest - alpine meadow 
340 TEMPERATE DESERT DIVISION 
| 341 j Semideserts 
I 342 | Semideserts and deserts 
M340 TEMPERATE DESERT MOUNTAINS 

pM341/ Semidesert - open woodland - coniferous forest - alpine meadow 

400 HUMID TROPICAL DOMAIN 

410 SAVANNA DIVISION 



[ 411 Open woodlands, shrubs, and savannas 
| 412 j Semi-evergreen forests 
|^| Deciduous forests 
M410 SAVANNA MOUNTAINS 

fwu ^ Open woodland - deciduous forest - coniferous forest - steppe or meadow 
Forest ■ steppe 

420 RAINFOREST DIVISION 

I 421 | Semi-evergreen and evergreen forests 
Everareen forests 



M420 RAINFOREST MOUNTAINS 

Evergreen forest - meadow or paramos 

INTRAZONAL REGIONS 



L 






Riverine forest 

Mountains with altitudinal zonation. These provinces are named 101 the spectrum 
of /ones from lower to upper (subnival); e.g.. semidesert coniferous forest 

alpine meadow